Affects the postgresql_psycopg2 backend only. We now don't use the
"RETURNING" syntax in SQL INSERT statements unless it's required by the
autocommit behaviour. This fixes an edge-case that could cause crashes
with earlier PostgreSQL versions, but the broader problem remains to be
fixed (which is #10509).
Fixed #10467. Refs #10509.
git-svn-id: http://code.djangoproject.com/svn/django/trunk@10065 bcc190cf-cafb-0310-a4f2-bffc1f526a37